1. Technical Field
The present invention relates to a scissor-type cutter having a movable knife that pivots to and away from a fixed knife, and to a printer having an automatic cutter and a paper exit of which the bottom edge is a substantially horizontal surface and from which the cut-off ends of recording medium (the cut paper) are discharged. More specifically, the invention relates to an automatic cutter whereby defective cuts resulting from adhesive squeezed out from the edges of label paper when the paper is cut do not occur, and to a printer having the automatic cutter.
2. Related Art
One type of label paper used for printing has an uncut label medium of the same constant width as the continuous liner backing to the surface of which the label medium is affixed by adhesive like a continuous tape. Such label paper is referred to as full-surface uncut label paper or continuous label paper, and is used to cut and print labels of different sizes. Printers having an automatic paper cutter for cutting the printed portion of the label paper may be used to produce labels using uncut label paper. The automatic cutter is disposed to the transportation path from the print head or printing position to the paper exit at the downstream end part in the transportation direction, and the printed label that is the cut-off portion of the label paper is discharged from the paper exit.
A scissor type automatic paper cutter that can be disposed in a printer is taught in Japanese Unexamined Patent Appl. Pub. JP-A-H09-19890. In the automatic cutter taught in JP-A-H09-19890 the fixed knife is disposed with the cutting edge facing up, and the movable knife pivots on a support pin at one end in the cutting direction of the movable knife between a standby position where a specific gap is formed between the cutting edge of the movable knife and the cutting edge of the fixed knife, and a cutting-completed position where the cutting edge of the movable knife and the cutting edge of the fixed knife overlap throughout the entire range of the cutting direction. A spring member that pushes the movable knife toward the fixed knife is attached to the support pin, and the compression force between the cutting edge of the movable knife and the cutting edge of the fixed knife is maintained to greater than or equal to the compression force required to cut the recording paper by means of this spring member. The label paper is inserted on the transportation path from the fixed knife side and the cut-off portion is discharged from the movable knife side.
The paper exit disposed to the automatic cutter or a printer with an automatic cutter must have a narrow opening so that foreign matter is not inserted from the outside, and is generally long and narrow in the cutting direction (the paper width direction). More specifically, the bottom edge of the paper exit is commonly positioned slightly below the cutting edge of the fixed knife and the top edge of the paper exit is positioned slightly above the cutting edge of the fixed knife so that the vertical size of the opening is reduced. When the movable knife moves toward the cutting-completed position with this configuration, however, the upstream side end part in the paper discharge direction of the cut-off portion is pushed below the bottom edge of the paper exit by the downward moving movable knife. The cut-off portion also becomes curled. As a result, when the movable knife returns to the standby position, the cut-off portion may spring up as a result of the resilience of the paper when the curled portion returns.
To prevent the cut-off portion from popping out from the paper exit, the bottom edge of the paper exit may have a substantially level stage that extends for a specific width in the cutting direction along the edge of the fixed knife slightly below the cutting edge of the movable knife at the cutting-completed position. Because the stage that determines the bottom edge of the paper exit in this configuration is positioned below the cutting edge of the movable knife at the cutting-completed position, the movable knife does not push the upstream end part of the cut-off portion down when cutting, the upstream end part of the cut-off portion is above the bottom edge of the paper exit and is not caused to curl. In addition, because cut-off portion is placed on the stage when cutting is completed, the cut-off portion rests stably. Rendering the bottom edge of the paper exit from which the cut-off portion is discharged by means of a substantially level stage is therefore beneficial.
However, when the bottom edge of the paper exit is determined by a stage surface that is positioned below the cutting edge of the movable knife when the movable knife has moved to the cutting-completed position of a scissor type automatic cutter, adhesive is squeezed from between the liner and the label and builds up on the stage surface when uncut label paper is cut because the uncut label paper is cut from one edge by the scissor action of the movable knife and the fixed knife. More specifically, because the compression force between the cutting edge of the fixed knife and the cutting edge of the movable knife is applied at the side of the support pin that is the pivot point of the movable knife, the compression force weakens to the other side in the cutting direction away from the support pin. As a result, when the label paper is cut, the adhesive between the liner and the label is pushed from the support pin side of the movable knife to the distal end while being squeezed between the fixed knife and the movable knife, and the adhesive sticks to the edge of the fixed knife and the cutting edge of the movable knife.
More particularly, because the adhesive is pushed out to the distal end side of the movable knife at the cutting end side, there is a tendency for a large amount of adhesive to stick at the distal end side of the movable knife. The adhesive that sticks to the cutting edge of the movable knife then moves gradually down from the movable knife due to gravity and sticks to the stage surface. The adhesive sticking to the edge of the fixed knife is also scraped down with the movement of the movable knife and builds up on the stage surface. When the adhesive accumulates on the stage, the accumulated adhesive gets between the cutting edge of the movable knife and the cutting edge of the fixed knife, interferes with cutting, and thus results in deficient cuts.